For the New World I'm working on presently, I'll be using the hybrid method of rust removal outlined here:
The twist this time is that I'm doing a series of partial soaks rather than containing water inside the fender well. Again, Oxalic Acid in a large, old garbage can is used. I check these every 30 to 60 minutes. I am especially looking for signs the solution is pulling up paint, but so far have been fortunate in that the paint is untouched.
I am basically soaking the fenders in sections. The reason for this is that the guards are riveted to the fenders rather than bolted. This means my options are to try to soak with the guards on, or else remove the guards by drilling out the rivets, then replacing with Riv-nuts or new rivets later. Since the rivets on these are not in bad shape, I would like to leave them
I also realize the guards are Cad-plated metal. As I noted earlier, Oxalic Acid pulls Cad plating right off the metal. That said, these guards have no real cad plating left. They are basically rusty. The soak will return them to bare metal, and then I have to weight my options of either leaving the metal bare (relic type status) or putting together a mild silver wash that will look the same as the previous Cad plating did. Either is a possibility, but for now the job is to remove the rust.
I also employed paper towels soaked in the solution to cover other areas. Eventually, all areas will be subjected to the soak, but this gives a little head start on the other areas.
The above cup appears to be filled with urine of some sort. Instead, it is Oxalic solution interacting with the rust on the seat clamp bolt, nut and washer. Again, I realize it was Cad plated, but there really is no Cad left on these, so it's time for a soak and rust removal. I believe I will leave these bare and just treat with a little WD40 to stave off moisture.
I realize there are some people who would not employ Oxalic Acid at all on these parts due to the Cad plating issue. They would rely on a pure mechanical means of rust removal (Dremel brush, copper/bronze wool, etc). I thought about that and actually tried it, but it really did not touch the rust on some of these parts, especially the fender braces. I've actually had the braces soaking for 2 evenings now, and am just now really making a dent in the rust that was there. These braces really were rusty. However, with Oxalic Acid, they will clean up.
I think I have another evening of soaking coming. They're not quite cleaned to satisfaction yet, or at least enough to the point that I would be sure a Dremel wire brush would totally finish the job. So, one more evening, I think.